Metal slugs and a method of producing the same



A ril 21, 1970 A'.'F. TASSARO 3,507,140

' METAL SLUGS AND A 'METOHD 0F PRODUCING THE SAME Filed March 24. 1957 THE.

lNl/EN TOR. ALFRED F. TASSARO Ar rarney I United States Patent 3,507,140 METAL SLUGS AND A METHOD OF PRODUCING THE SAME Alfred F. Tassaro, New Kensington, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a

corporation of Pennsylvania Filed May 24, 1967, Ser. No. 640,923

Int. Cl. B21d 31/02, 31/00, 28/00; B21c 37/02 U.S. Cl. 72-327 3 Claims ABSTRACT OF THE DISCLOSURE Tubular products having a necked end portion, such as containers having a dispensing nozzle projecting from one end, may be impact extruded from pierced metal slugs. A slug that may be used for this extrusion is a dished slug having a pierced aperture located centrally therein which may be provided by piercing and blanking the slug from a sheet of metal by forcing a punch having a piercer projecting from its end, through the sheet and into a female die.

BACKGROUND OF THE INVENTION This invention relates to slugs especially adapted to be impact extruded into a tubular product having an integral necked end portion, and to a method of providing the slugs. In the extrusion of tubular products having a necked portion at one end, such as collapsible tubes or other containers with a tubular orifice or a dispensing nozzle projecting from one end, the extrusion punch typically has an integral, thin mandrel or nose portion projecting from its center. The function of this thin mandrel is to co.-act with a corresponding central orifice in the female extrusion die to form the necked end portion or dispensing nozzle on the extruded product. This mandrel is frequently quite small in relation to the body of the punch and is subjected to considerable stress during the extrusion of the product, especially if the mandrel must pierce the slug during the extrusion operation. Consequently, unless the stresses on the mandrel are minimized, extrusion punches will be prone to failure by fracturing or breaking of the mandrel from the end of the punch.

Heretofore, the usual method of minimizing stress to reduce the incidence of failure of the mandrel has been to blank or drill a small section of metal out of the center of the slug to produce a hole through the slug, so as to permit relatively free passage of the mandrel therethrough. Blanking or drilling a center section out of the slug, however, means that the metal in this section is lost except as it may be salvaged as scrap.

SUMMARY OF THE INVENTION AND OBJECTS I have discovered that, by providing a pierced slug in which metal has been moved divergently and in advance of a piercing tool without disjoining a substantial amount of metal from the slug, a tubular product with a necked end portion may be extruded from this pierced slug economically.

An object of this invention is to provide a pierced slug adapted to be impact extruded economically into a tubular product.

Another object of this invention is to provide a method of producing a pierced slug adapted to be impact extruded into a tubular product having a necked portion, in which there will be a maximum utilization of metal.

The above and other objects and advantages of this invention will be apparent from the following description with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view of a punch and die assembly that may be employed in the practice of the invention showing a metal sheet in place therein and a slug sheared from the sheet.

FIG. 2 is a vertical cross-sectional view showing an extrusion punch and female extrusion die that may be used to impact extrude a slug made in accordance with this invention into a tubular product.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, a preferred embodiment of a die set comprised of a punch .10 and female die 11 for performing this invention is shown with a sheet of metal 12 supported on the die 11 and a pierced slug 13 sheared from the sheet 12. In this die set the female die 11 has a die opening 14 generally corresponding to the shape of the slug 13 that is to be provided. This opening 14 extends completely through the die 11 and has, except for an inwardly projecting lip .18 defining the die orifice around its upper periphery, a uniform diameter throughout its depth.

The punch 10 is comprised of a main body portion 15 and an integral piercing tool or piercer 16 projecting from its center. The body portion 15 of the punch corresponds in cross-section to the shape of the slug 13 to be provided and is given a slide fit with the lip 18 in the die 11. To facilitate piercing of the sheet 12, the piercer 16 on the punch 10 has a pointed end 17 as seen in FIG. 1. The length of this pointed end 17 is not critical, as the taper could extend over the entire length of the piercer. Preferably, however, the taper extends over only a portion of the piercer as shown so as to be less prone to fracture. As for the overall length of the piercer 16, in the preferred embodiment of this invention, it is slightly longer than the thickness of the slug 13 to be provided. As will be seen in the operation of the invention, this permits the piercer 16 to break the bottom surface of the slug 13 without disjoining a substantial amount of metal from the slug 13.

The female extrusion die 22 and extrusion punch 27 shown in FIG. 2 represent an example of an extrusion die set that can be used in extending the slug 13 into a tubular product. As shown, the female die 22 has a die cavity corresponding to the external shape of the tubular product 25, and the punch 27 generally corresponds to the bore within the tubular product. The thin mandrel 23 on the punch 27 and central die orifice 24 in the female die 22 are designed to form the necked portion 26- on the final product 25.

In the practice of the invention, the metal sheet 12 or plate stock is ordinarily comprised of a relatively ductile metal such as lead, tin, or aluminum or alloys of these metals. This sheet is first supported against or over the female die 11, leaving an unsupported portion over the die opening 14. The punch 10 with the piercer 16 projecting from its center is then forced through the unsupported portion of the sheet 12 and through the die orifice 18. The piercer 16 is thereby first applied against the sheet 12 and acts to move metal divergently and forwardly in advance of its point 17 to produce a dished portion having a concave upper surface 20 and a corresponding convex lower surface 21, and also to produce a pierced aperture 19 centrally located in this dished portion.

Since the piercing tool 16 is pointed, and since it is only slightly longer than the thickness of the dished portion of the sheet, only the end of the point 17 will completely penetrate the sheet before the body of the punch engages the upper surface of the sheet 12. Consequently, the pierced aperture 19 will correspond to the shape of the piercer 16 and the piercer point 17 to the extent that the walls of the aperture converge, as does the piercer point, as they approach the bottom face 21 of the dished portion of the sheet, to define a smaller hole in the bottom face of the sheet than in the top face of the sheet. In this way, very little, if any, metal will be disjoined from the sheet by the piercer 16, since the lower surface of the sheet will be broken to produce only. a small hole therethrough. Instead of disjoining the metal, the piercers movement of the metal divergently and in advance of the point will form a small downwardly domed section around the hole in the bottom of the sheet. The metal in this domed section along with the rest of the slug 13 is available to be extruded into the tubular product and is not wasted. If the piercer were longer, it would penetrate the sheet further and would tend to burr the domed section outwardly and possibly disioin or tear this metal from the sheet so that the metal so lost would not be available for subsequent extrusion.

The optimum length of the piercer 16 for a given slug size may be readily determined. As mentioned above, if the piercer 16 is too short it will not completely pierce the sheet 12, and if it is too long it will tend to disjoin or sever metal from the sheet 12 around the bottom of the aperture 19 while producing a relatively large opening through the bottom face of the sheet. In practice, this bottom opening may be smaller than the thin mandrel 23 on the extrusion punch 27, so that there will be an interference fit to center the slug as it is extruded, as shown in FIG. 2. It is noted also that a piercer shaped as shown in FIG. 1, with only the lower portion 17 being pointed, is preferable to one tapered over its entire length because the aperture produced thereby will have an interference fit with the mandrel for only a relatively short distance in the aperture and therefore provide centering while creating a minimum of resistance to passage of the mandrel.

Once the end of the body portion of the punch engages the sheet and continues into the die opening 14, the co-acting peripheral edges of the punch and the lip 18 around the mouth of the die will shear the slug 13 from v the sheet 12. Inasmuch as the piercer 16 is disposed in the center of the punch 10, the pierced aperture 19 will likewise be centered in the slug 13 sheared from the sheet 12. During the shearing, the pressure exerted by the convex end of the body portion of the punch will produce an opposing concave upper surface 20 on the slug 13. The juncture of the piercer 16 and the body portion 15 of the punch 10 may be relatively abrupt so as not to cause unnecessary deformation of the slug 13. It is noted, however, that the size and shape of the piercer 16, the diameter of the slug 13 to be provided, the thickness of the sheet 12, and the softness of the metal in the sheet will also aifect the degree of deformation of the slug 13. For example, if the sheet is made of relatively soft metal, or if the piercer has a diameter that is large in relation to the diameter and thickness of the slug to be produced, the slug might tend to deform more readily.

Although not essential to the utilization of slugs produced in accordance with this invention, the pierced slugs are usually lubricated with a lanolin, wax or other lubricant prior to impact extrusion. This lubrication not only increases the life of the extrusion dies, but also contributes to producing an extruded product having a smooth finish. Lubrication can be applied by several methods including dipping or spraying to provide a film of lubricant over the entire surface of the slug 13 and on the Walls of the aperture 19 in the slug. Lubricant in the aperture 19 is particularly beneficial to minimize the resistance to the passage of the mandrel 23 on the extrusion punch and permit effective centering of the slug in the extrusion dies.

After the slug is lubricated, it is positioned, concave side up, in the female extrusion die 22 shown in FIG. 2, and impact extruded between the extrusion punch 27 and the female extrusion die 22 into the tubular product 25. In this extrusion, the mandrel 23 penetrates the aperture 19, centers the slug, and then as the extrusion punch 27 continues to the bottom of its stroke and in cooperation with the cenral orifice 24 in the female die 22, forms the necked portion 26 on the tubular product 25. The metal from the slug 13 is extruded both downwardly around the mandrel 23 to form the necked portion 26, and upwardly around the body of the extrusion punch 27 to form the walls of the tubular product 25. No metal need be wasted except for that which may be subsequent- 1y trimmed from the ends of the tubular product.

In order to control the metal flow and to prevent an excess of metal from being extruded downwardly, the central orifice 24 may be given a smaller diameter or restriction near the bottom of the female die 22. Depending on the length of the necked portion 26 that is desired, this restriction or narrowing of the central orifice 24 may be located accordingly. After the tubular product 25 has been extruded, it is then stripped from the extrusion punch 27, trimmed at both ends, cleaned, and is ready for use.

It is thus seen that in the practice of this invention there is a minimum of scrap from the original sheet 12. Virtually all of the metal in the area of slug is extruded into the final tubular product. Consequently, using the method described herein, a thinner sheet of metal can be used to produce the same tubular product as could be produced using the heretofore known methods wherein the center section of the slug was removed. Additionally, the slug is centered in the extrusion dies with a minimum of resistance to the passage of the mandrel through the slug.

While the invention has been described, and a preferred practice and embodiment have been set forth, it will be obvious to those skilled in the art that many modifications of the invention are possible without departing from the scope thereof.

What is claimed is:

1. A method of producing a slug especially adapted to be impact extruded into a tubular product having an integral necked end portion comprising the steps of:

(a) supporting a sheet of metal;

(b) piercing said sheet to move the metal thereof divergently and forwardly to produce, without disjoining a substantial amount of metal from said sheet, a dished portion in said sheet with a pierced aperture located centrally therein with the walls of said pierced aperture converging as they approach the bottom face of said dished portion to define a smaller hole in said bottom face than in the top face of said dished portion; and

(c) shearing from said sheet a slug of metal consisting of said dished portion with said pierced aperture therein.

2. A method of producing a slug especially adapted to be impact extruded into a tubular product having an integral necked end portion comprising the steps of:

(a) supporting a sheet of metal around the periphery of an unsupported portion thereof generally corresponding to the shape of the slug to be produced;

(b) piercing said sheet by applying a piercing tool thcreagainst centrally of said unsupported area to move the metal thereof divergently and in advance of said tool to produce, without disjoining a substantial amount of metal from said sheet, a dished portion in said sheet with a pierced aperture located centrally therein with at least the lower portion of the walls of said pierced aperture converging toward the bottom face of said dished portion to define a smaller hole in said bottom face than in the top face of said dished portion; and

(c) shearing from said sheet a slug of metal corresponding to the unsupported portion aforesaid and having said pierced aperture therein.

3. The method set forth in claim 2 in Which said sheet is supported against a female die having a die orifice generally corresponding to the shape of said slug to be produced, and said piercing and said shearing are efiected by forcing through said sheet and into said die orifice a punch having an integral piercer projecting from the center thereof.

References Cited UNITED STATES PATENTS Mezger 72-377 Lee 72-325 Hasselquist 72-327 Howard et a1. 29-161 Fransson 10-86 Lanius 10-86 CHARLES W. LANHAM, Primary Examiner E. M1 COMBS, Assistant Examiner U.S. Cl. X.R. 

